The disposal of wastes both from municipal and industrial sources, such as trash, rubbish, garbage, animal wastes, agricultural wastes, and waste of plastic processing operations is rapidly becoming of immense national concern. The cost of disposal ranks third behind public schooling and highways as municipal expense in the United States.
It is estimated that each individual in the country generates between 4 and 6 pounds of waste per day, that the industrial output is equivalent to approximately 5 pounds of solid waste per person per day. Previous methods of mass waste disposal, such as landfill, are becoming impossible, while others such as incineration are costly and result in air pollution problems.
A vast majority of the waste which is presently disposed of contains products which are immediately recyclable back into the economy or products into which the waste can be converted for recycle back to the economy. Directly recyclable constituents are the various metals present, such as aluminum and steel, and glass. For the most part, the organic solid waste fraction is subjected to flash pyrolysis as an operation independent of recovery of the directly recyclable inorganic fraction and any organic portion recovered as pulp. Flash pyrolysis yields carbon containing solid residue of pyrolysis or char, condensible pyrolytic oils and combustible gases.
In the flah pyrolysis process, particulate solid organic waste which includes particulate inorganic constituents, a particulate source of heat, the carbon containing solid residue of pyrolysis and/or an inorganic heat source formed by decarbonization of the carbon containing solid residue of pyrolysis, and a carrier gas which is nondeleteriously reactive with respect to the pyrolysis products, are combined and passed under turbulent flow conditions through a pyrolysis zone maintained at a temperature from about 600.degree. to about 2200.degree. F or in the instance of the inorganic heat source, below its fusion temperature, i.e. 1425.degree.-1450.degree. F. The preferred temperature range is from about 800.degree. to about 1350.degree. F. The carbon containing solid residue of pyrolysis with the solid source of heat after separation from the pyrolytic oils and gaseous components is reheated as part of a loop, by total or partial combustion and decarbonized to the particulate source of heat for recycle back to the pyrolysis zone.
In the pyrolysis process, the solid organic waste exists as discrete particles having a diameter less than 1 inch, and are preferably of a size less than about 5 mesh, preferably less than 8 mesh. The particulate source of heat, e.g. the carbon containing solid residue of pyrolysis (char) and/or the inorganic heat source (ash) formed by carbonization of the former, for ease of mass transport, is generally of a particle size in the range from about 10 to about 1,000 microns. Although any carrier gas which is nondeleterious, i.e., essentially oxygen free, to the products of pyrolysis may be used as a transport gas for both the organic solid waste and the particulate source of heat, it is preferred for expediency in the process to use the gases which are the byproducts of the pyrolysis operation itself.
In the process, the organic solid waste which is normally at a temperature from ambient to about 100.degree. F must rapidly be heated to the pyrolysis temperature. Heating of the organic solid waste occurs predominately by solids to solids contact with the particulate inert source of heat. Thorough mixing under solid transport conditions within a fraction of a second becomes essential.
The present invention is directed to an improved pyrolysis reactor which enables a continuous pyrolysis reaction under flow conditions with a single pass of the particulate organic feed in contact with the particulate source of heat within a relatively short chamber at residence times of a fraction of a second.